Contact



Patented Dec. 20, 1938 UNITED STATES CONTACT Chester Peterson,Maplewood, N. J., assignor to The H. A. Wilson Company, a corporation ofNew Jersey No Drawing. Application April 24, 1937,. Serial No. 138,755

4 Claims.

This invention relates to electrical circuit breaker mechanisms, and isconcerned more particularly with contacts for use in such apparatus,which are made of a novel composition and give better results forspecific purposes than contacts of the materials heretofore available.

Contacts employed in electrical circuit breaker devices are made ofvarious metals, alloys, or metallic compositions selected because oftheir physical and electrical characteristics. Among the desiredcharacteristics are relatively high current carrying capacity, lowcontact resistance, and durability and resistance to mechanical wear,but in specific applications, certain characteristics may be so muchmore important than others as to determine the selection of theparticular materials. Thus, in circuit breaker mechanisms operating ondirect current, the current and voltage conditions in the circuit beingso made and broken are frequently such that various contact materialssuitable for other uses can not be employed because they have a tendencyto build up and stick together. These changes in the contacts interferewith the proper operation of the mechanism and may require frequentrepair or replacement of the contact members.

The tendency of contacts to build up and stick together in directcurrent apparatus is especially pronounced when both points are made ofthe same material as it is found that with similar contacts made ofmaterials heretofore ordinarily used, such for example as fine silver, ahigh sharp local peak is produced on one point and a corresponding deepcavity or crater on the other.

When such a peak and crater are formed in an apparatus in which thepoints move together and apart with a shearing or rubbing action, as isfrequently the case, the peak enters the crater and-the points interlockand stick even though there is no action comparable with welding.

The present invention is accordingly directed to the provision of anovel contact which may be used to great advantage in those forms ofcircuit breaker mechanism in which the tendency of the contacts to buildup and stick together must be minimized, an example of such a contactbeing an automotive voltage regulator.

In my copending application, Serial Number 138,754 filed April 24, 1937,I have disclosed contact members made of a silver-manganese alloy whichmay be used advantageously in circuit breaker apparatus of the typereferred to, and while those contacts are satisfactory in operation, thepresent high cost of silver renders their u use somewhat expensive.

I have found, however, that contacts giving equally good, and in somecases better, results may be made by adding a diluent to thesilvermanganese alloy of the application mentioned. This diluent may beone or more of the members of the group made up of copper and cadmium,and the results obtained from its use depend on the nature and amount ofthe diluent present in the contact members. I

In general, a contact of the invention contains 0 silver ranging fromabout to about 97%, manganese ranging from about 2% to about 20%, andthe remainder consisting of one or both members of the group above setforth. A preferred composition contains about silver, 15 about 5% toabout 15% manganese, and the diluent forming the remainder, and aspecific composition which has been found to give good results containsabout 80% silver, about 10% manganese, and about 10%cadmium. The use .0of cadmium in the diluent is highly desirable as this ingredient appearsto have the characteristic of quenching arcing.

In making up a composition for use in the new contact, various factorsare to be taken into 5 account. Thus, it may be said generally that anincrease in the amount of manganese within the limits specifiedincreases the antisticking properties of the contact and this is true,in general, of the amount of the diluent. Similarly, 30 an increase inthe amount of diluent results in an increase in economy.

In the use of the diluent consisting of copper, cadmium, ora combinationof both, total amounts up to about 23% may be employed and 5 the use ofthese materials in place of silver make available substantial economieswithout any important loss of the desired properties.

In all instances, the amount of manganese present should be notsubstantially less than 2%, 0 and an amount considerably in excess ofthat is preferred. Also, the new contact may be made of an alloycontaining manganese in excess of 20%, but a manganese content exceeding20% is not desirable. Similarly, the ranges of the 5 amounts of themembers of the class of metals making up the diluent are not fixed butthose given are the most desirable for ordinary purposes.

I claim: 60

1. A contact for electrical circuit breaker mechanisms composed of analloy of silver in pre-' ponderating amount, manganese, and a diluentconsisting of at least one member of the class made up of copper andcadmium.

2. A contact for electrical circuit breaker mecbaniamacompoaedoianalloyotlilverinan amount ranging from about 75% to about 95%,manganese in an amount ranging from about 2% to about 20%, and theremainder a diluent consisting of at least one member of the class madeup oi copper and cadmium.

- 8. A contact for electrical circuit breaker mechanisms composed 01' analloy of a prepondentin: amount oi silver. a less amount of man- :aneae,and a diluent consisting of at least one member of the class made up ofcopper and cadmium in an amount ranging from about 2% to about 23%.

4. A contact for electrical circuit breaker mechanisms, composed ofabout 80% silver, about 10% manganese. and about 10% cadmium.

CHESTER. PETERSON.

